High density bundled optical fiber cable with preconnectorized drop points

ABSTRACT

Embodiments of a bundled optical fiber cable are provided. Included therein is a central cable unit spanning a first length from a first end to a second end. The central cable unit has a first plurality of optical fibers disposed within a cable jacket. The bundled optical fiber cable also includes at least one optical fiber drop cable wound around the cable jacket of the central cable unit. Each optical fiber drop cable spans a second length from a first end to a second end. Further, each optical fiber drop cable includes one or more optical fibers disposed within a buffer tube. The first end of each optical fiber drop cable is substantially coterminal with the first end of the central cable unit, and the first length spanned by the central cable unit is longer than the second length spanned by each of the optical fiber drop cables.

PRIORITY APPLICATION

This application is a continuation of U.S. application Ser. No.17/122,012, filed Dec. 15, 2020, which is a continuation ofInternational Application No. PCT/US2019/038876 filed on Jun. 25, 2019,which claims the benefit of priority to U.S. Application No. 62/690,089,filed on Jun. 26, 2018, and U.S. Application No. 62/722,307, filed onAug. 24, 2018, the content of each of which is relied upon andincorporated herein by reference in their entirety.

BACKGROUND

The disclosure relates generally to optical fiber cables and moreparticularly to optical fiber cables that have drop cables that runalong at least a portion of the length of a main distribution cable.Optical fiber cables are used to transmit data over distance. Generally,large distribution cables that carry a multitude of optical fibers froma hub are sub-divided at network nodes, which are further sub-divided,e.g., to the premises of individual subscribers. Generally, thesesubdivisions involve splicing a cable tether into a main distributionline. Cable splicing at specific locations along a main distributionline is a delicate and time consuming process that requires preciseplacement of the cable tether and that involves the risks of cutting thewrong fibers and providing environmental exposure to the cable interior.

SUMMARY

In one aspect, embodiments of the disclosure relate to a bundled opticalfiber cable. The bundled optical fiber cable includes a central cableunit spanning a first length from a first end to a second end. Thecentral cable unit has a first plurality of optical fibers disposedwithin a cable jacket. The bundled optical fiber cable also includes atleast one optical fiber drop cable wound around the cable jacket of thecentral cable unit. Each of the at least one optical fiber drop cablespanning a second length from a first end to a second end. Further, eachof the at least one optical fiber drop cable includes one or moreoptical fibers disposed within a buffer tube. The first end of each ofthe at least one optical fiber drop cable is substantially coterminalwith the first end of the central cable unit, and the first lengthspanned by the central cable unit is longer than the second lengthspanned by each of the at least one optical fiber drop cable.

In another aspect, embodiments of the disclosure relates to a method ofpreparing a bundled optical fiber cable. In the method, a central cableunit having a first end and a second end is provided. The central cableunit includes a first plurality of optical fibers disposed within acable jacket. Further, at least one optical fiber drop cable is woundaround the cable jacket of the central cable unit beginning at the firstend and ending prior to reaching the second end. Each of the at leastone optical fiber drop cable comprises one or more optical fibersdisposed within a buffer tube.

Additional features and advantages will be set forth in the detaileddescription which follows, and in part will be readily apparent to thoseskilled in the art from the description or recognized by practicing theembodiments as described in the written description and claims hereof,as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description are merely exemplary, and areintended to provide an overview or framework to understand the natureand character of the claims.

The accompanying drawings are included to provide a furtherunderstanding and are incorporated in and constitute a part of thisspecification. The drawings illustrate one or more embodiment(s), andtogether with the description serve to explain principles and operationof the various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts partial perspective view of a bundled optical cable,according to an exemplary embodiment.

FIG. 2 depicts a cross-sectional view of the bundled optical cable ofFIG. 1 .

FIG. 3 depicts a detail view of a drop cable, according to an exemplaryembodiment.

FIG. 4 depicts a rolled-ribbon drop cable, according to an exemplaryembodiment.

FIG. 5 depicts a cross-sectional view of another embodiment of a bundledoptical cable, according to an exemplary embodiment.

FIG. 6 depicts an exemplary embodiment of a drop cable having rodentprotection, according to an exemplary embodiment.

FIG. 7 depicts an exemplary deployment for the bundled optical cableincluding electrical drop cables, according to an exemplary embodiment.

FIG. 7A depicts an exemplary bundled optical cable including electricaldrop cables, in accordance with aspects of the present disclosure.

FIG. 7B depicts an exemplary bundled optical cable including anelectrical drop cable, in accordance with aspects of the presentdisclosure.

FIG. 8 is a graph of laylength plotted against the ratio betweenlaylength and pitch circle for bundled optical fiber cables havingvarious central cable unit diameters.

FIG. 9 depicts a drop cable separated from the bundled optical fibercable at a drop location, according to an exemplary embodiment.

DETAILED DESCRIPTION

Referring generally to the figures, various embodiments of a bundledoptical fiber cable are provided. The bundled optical fiber cableincludes a central cable unit and at least one drop cable wound aroundthe distribution cable. Unlike other cable tethers, the drop cables ofthe bundled optical fiber cable are not spliced into the central cableunit. That is, the central cable unit and each drop cable run inparallel from each of their starting ends until each drop cable reachesits predetermined drop point. In this way, the central cable unit actsas an “express line” for transmitting data from node to node, and eachdrop cable provides data to a particular delivery point along the lengthof the cable between nodes. Various exemplary embodiments of a bundledoptical fiber cable are described herein; however, these exemplaryembodiments should be considered illustrative and non-limiting.

FIG. 1 depicts an embodiment of a bundled optical fiber cable 10 in apartial sectional view taken over a portion of the length of the bundledoptical fiber cable 10. As can be seen, the bundled optical fiber cable10 includes a central cable unit 12 and a plurality of drop cables 14that are wound around the outside of the central cable unit 12. Inembodiments, the drop cables 14 are helically wound around the centralcable unit 12. For example, in embodiments, the drop cables 14 may havean S winding or a Z winding around the central cable unit 12.Additionally, in embodiments, the drop cables 14 may have an SZ windingaround the central cable unit 12.

In embodiments, the drop cables 14 are held to the central cable unit 12only via the winding, which allows the drop cables 14 some degree ofmovement longitudinally along the length of the central cable unit 12during bending of the bundled optical fiber cable 10. In embodiments,the laylength of the winding (i.e., the length required for the dropcable 14 to make a complete revolution around the central cable unit 12)is a function of the ratio between the laylength LL and a pitch circlePC (as shown in FIG. 2 ). With reference to FIG. 2 , the pitch circleruns through the center of each drop cable 14 and, thus, has a diameterextending from the center of a first drop cable 14 to the center of asecond drop cable 14 directly opposite the first drop cable 14.Therefore, the diameter of the pitch circle is equal to the outerdiameter D bundled optical fiber cable 10 minus the outer diameter d ofone drop cable 14. In embodiments, the laylength of the drop cables 14is selected such that the ratio LL/PC is 20 or less. In otherembodiments, the laylength of the drop cables 14 is selected such thatthe ratio LL/PC is 17.5 or less, and in still other embodiments, thelaylength is selected such that the ratio LL/PC is 15 or less. FIG. 8depicts a chart showing the laylength and ratio LL/PC for a variety ofbundled optical fiber cables 10 having central cable units 12 with outerdiameters of from 5 mm to 25 mm. In the exemplary embodiments consideredin FIG. 8 , each of the central cable units 12 were considered usingdrop cables having an outer diameter of 4.8 mm. Line A is located at aratio LL/PC of 15, and line B is located at a ratio LL/PC of 20. As canbe seen, the maximum allowable laylength while remaining under a givenratio LL/PC increases as the central cable unit OD increases. Thus, forexample, a bundled optical fiber cable 10 having a central cable unit 12with a 5 mm outside diameter can have a laylength of about 150 mm for anLL/PC of 15 or of about 200 mm for an LL/PC of 20. A lower laylengthcorresponds to tighter coils of the drop cables 14 around the centralcable unit 12, which increases the length of the drop cables 14necessary for a given length of the central cable unit. Further,processing line speed is slower at lower laylengths because of thetighter coiling. Thus, in embodiments, the laylength is maintained closeto the allowable LL/PC ratio to reduce extra fiber length and tomaintain a higher processing line speed.

In embodiments, bands are placed at various intervals along the lengthof the bundled optical fiber cable 10 to keep the drop cables 14 wrappedaround the central cable unit 12. In certain embodiments, the bands arewelded polyethylene bands. In another embodiment, webbing, such as apolyethylene web ribbon, is provided around the drop cables 14 to keepthe drop cables 14 wrapped around the central cable unit 12.

As will be appreciated from the discussion provided later herein, inembodiments, the drop cable 14 each have different lengths and run onlyso far as to reach their desired drop location. The central cable unit12 spans at least as long as the longest drop cable 14. However, each ofthe drop cables 14 and the central cable unit 12 has substantially thesame beginning point. Put differently, each of the drop cables and thecentral cable unit 12 begin at the substantially the same location butend at different locations, thereby causing the drop cables 14 and thecentral cable unit 12 to span different cable lengths. As discussedherein, the “span” length of the drop cables 14 refers to the distanceover which the drop cable 14 is able to run from its beginning locationto its ending location and not to the actual length of the drop cable 14itself. That is because, in embodiments, winding the drop cable 14around the central cable unit 12 will make the actual length of the dropcable 14 longer than the span length.

FIG. 2 provides a detailed cross-sectional view of the bundled opticalfiber cable 10. As can be seen, the drop cables 14 are substantiallyevenly spaced around the circumference of central cable unit 12. In theembodiment depicted, there are thirteen drop cables 14. In embodiments,as few as a single drop cable 14 can be provided around the centralcable unit 12. In other embodiments, as many as twenty-four drop cables14 can be provided around the central cable unit 12. Further, as will bediscussed more fully below, the drop cables do not all need to containoptical fibers. For example, in embodiments, the drop cables can be“dummy cables” that do not contain any data or electrical transmissionelement but which provide structural support around the cable.Additionally, the drop cables can include electrical transmissionelements, such as wires.

In general, the number of drop cables 14 that can be provided around thecentral cable unit 12 depends on size of drop cables 14, size of thecentral cable unit 12, and any external limiting factors for overallsize (e.g., a 2″ duct which houses the bundled optical fiber cable 10).In an exemplary embodiment, the central cable unit 12 has an outerdiameter of 20 mm, and the drop cables 14 each have an outer diameter dof 4.8 mm. In this exemplary embodiment, fifteen drop cables 14 are ableto fit around the central cable unit 12. The outer diameter D of thebundled optical fiber cable 10 according to this exemplary embodiment isapproximately 30 mm. Considering other components of the cable, such asthe connectors for the drop cables 14 and any protective covers to holdthe connectors to the bundled optical fiber cable 10, this exemplaryembodiment would provide a fill ratio of about 85% for a 2″ circularduct. In general, the size of the bundled optical fiber cable 10,including the number of drops 14, is only limited based on the size ofthe equipment used for installing the bundled optical fiber cable 10 andthe available duct space for carrying the bundled optical fiber cable10. Thus, for example, a 30 mm center cable unit 12 with twenty dropcables 14 could be carried in a 3″ duct. With respect to available ductspace, in embodiments, the diameter D of the bundled optical fiber cable10 is configured such that the cross-sectional area of the bundledoptical fiber cable 10 at its widest point is no more than 85% of thecross-section area of the duct into which the bundled optical fibercable 10 is installed.

As used herein, the diameter D referenced with respect to the embodimentof FIG. 2 refers to the diameter of a hypothetical circle defined by theoutermost extents of the drop cables 14. As viewed from thecross-section of FIG. 2 , the bundled optical fiber cable 10 is definedby a larger, central circle surrounded by smaller, outer circles. Thus,the actual outermost surface of the bundled optical fiber cable 10undulates moving from drop cable 14 to drop cable 14 around thecircumference. Accordingly, the actual cross-sectional width of thebundled optical fiber cable 10 varies at different positions measuredaround the circle.

Referring now to the structure of the bundled optical fiber cable 10 asshown in FIG. 2 , the central cable unit 12 includes a cable jacket 16having an inner surface 17 and an outer surface 18. The inner surface 18defines a cable bore 19 within which a plurality of optical fibers 20are disposed. The optical fibers 20 can be arranged in a variety ofsuitable ways within the central cable unit 12. In the embodimentdepicted, the optical fibers 20 are arranged in a stack 21 of multipleribbons 22. In particular, the optical fibers 20 are arranged into astack 21 of sixteen ribbons 22 having a plus-shaped cross-section. Thesixteen ribbons 22 include an upper stack section 23, a middle stacksection 24, and a lower stack section 25. In embodiments, the upperstack section 23 and the lower stack section 25 contain the same numberof optical fibers 20 and/or ribbons 22. Also, in embodiments, the middlestack section 24 includes at least twice the number of optical fibers 20per ribbon 22 as compared to the upper stack section 23 and/or the lowerstack section 25. Further, in embodiments, the middle stack sectionincludes as least twice as many ribbons 22 as compared to the upperstack section 23 and/or the lower stack section 25. In an exemplaryembodiment shown in FIG. 2 , the upper stack section 23 and the lowerstack section 25 each have four ribbons 22 of twelve optical fibers 20.The middle stack section 24 in the embodiment depicted has eight ribbons22 of twenty-four optical fibers 20. Thus, in the embodiment depicted,the total number of optical fiber 20 is 288. In embodiments, a singlestack can contain up to 864 optical fibers 20. As shown in FIG. 2 , thestack 21 is surrounded by a stack jacket 27, which, in embodiments, mayprovide color coding for multiple-stack configurations (discussed below)and/or water-blocking properties.

In embodiments, multiple stacks 21 can be provided in the cable bore 19.In an exemplary embodiment, the cable bore 19 contains six stacks 21 of288 optical fibers 20 for a total of 1728 optical fibers 20. In anotherembodiment, the cable bore 19 contains twelve stacks 21 of 288 opticalfibers 20 for a total of 3456 optical fibers 20. In embodiments havingmultiple stacks 21, the stacks 21 may be wound around a centralstrengthening member, such as a glass-reinforced plastic member. As willbe understood, the number of optical fibers 20 provided in the centralcable unit 12 has a bearing on the overall size of the bundled opticalfiber cable 10. Thus, the number of optical fibers 20 that can beincluded in the central cable unit 12 may be dictated by the particularinstallation parameters. Central cable units of the type described areavailable from Corning Incorporated, Corning, N.Y., such as thosemarketed under the trademark RocketRibbon™.

Moreover, while FIG. 2 depicts the optical fibers 20 arranged in ribbons22 that are further arranged into stacks 21, the cable bore 19 couldinstead include a plurality of loose optical fibers 20 or a plurality ofoptical fibers 20 grouped into multiple buffer tubes. In the latterembodiment, the optical fibers 20 in the buffer tubes can, for example,be arranged in ribbons 22, or the optical fibers 20 can, for example, bein a loose tube configuration. Further, each buffer tube can contain thesame or a different number of optical fibers 20. Central cable units 12of the type described in this paragraph are available from CorningIncorporated, Corning, N.Y., such as those marketed under the trademarksALTOS®, SST-Ribbon™, and SST-UltraRibbon™. Additionally, in embodiments,the central cable unit 12 is configured to have a small diameter D forinstallation in small ducts (e.g., 2″ or less). Such central cable units12 of this type are available from Corning Incorporated, Corning, N.Y.under the trademark MiniXtend®.

As can also be seen in the embodiment of FIG. 2 , the cable jacket 16includes two strength members 26. In embodiments, each strength member26 is made of glass-reinforced plastic or metal. Further, while twostrength members 26 are depicted, embodiments of the central cable unit12 can include no strength members 26 or up to four strength members 26.In embodiments, an additional toning member may be embedded in the cablejacket 16 along with the strength members 26. The toning member isselected to be metal to allow for cable location via toning, which is atechnique where a signal is sent over the toning member of a buriedoptical fiber cable such that the signal can be detected above groundfor the purpose of locating the optical fiber cable.

FIG. 3 depicts an embodiment of a drop cable 14. In the embodimentdepicted in FIG. 3 , the drop cable 14 is a loose tube cable in whichthe optical fibers 20 are contained in a buffer tube 28. The buffer tube28 has an interior surface 29 defining a bore 30 in which the opticalfibers 20 are contained, and the buffer tube 28 has an exterior surface31 around which strengthening yarns 32 may optionally be wound. The dropcable 14 also includes a jacket 34 around the buffer tube 28. Inembodiments, a ripcord 36 is embedded in the jacket 34 to provide accessto the interior of the drop cable 14.

In the embodiment shown in FIG. 3 , the drop cable 14 includestwenty-four optical fibers 20. However, the drop cable 14 can include,e.g., from one optical fiber 22 up to thirty-six optical fibers 20 inembodiments depending on the particular needs of the installation.Further, the drop cable 14 depicted in FIG. 3 is a loose tube cable. Inother embodiments, the optical fibers 20 are arranged in one or moreribbons within the buffer tube 28. In a particular embodiment shown inFIG. 4 , the optical fibers 20 are arranged in a rollable ribbon 38. Insuch embodiments, the optical fibers 20 are joined with a web or matrixmaterial that allows the optical fibers 20 to be rolled or bent into avariety of different positions. Rollable ribbons of the type suitablefor use as a drop cable 14 are described in U.S. Publication No.2017/0031121, published on Feb. 2, 2017, for application Ser. No.15/216,757, filed on Jul. 22, 2016, the contents of which areincorporated herein by reference in their entirety. Rollable ribbons 38provide the ability to splice multiple fibers in a single process alongwith the ability to fit the rollable ribbon 38 in a smaller buffer tube28.

The bundled optical fiber cable 10 as shown in FIG. 2 can include avariety of different drop cables 14 wound around the central cable unit12, including at least one drop cable 14 as shown in FIG. 3 , at leastone drop cable 14 as shown in FIG. 4 , and/or at least one drop cable ofa variety of other types described herein or known to those of ordinaryskill in the art.

FIG. 5 depicts another embodiment of a bundled optical fiber cable 10′.In the embodiment of FIG. 5 , the central cable unit 12 is surrounded bya plurality of drop cables 14 that are further surrounded by a bundlejacket 40. The exterior surface 41 of the bundle jacket 40 defines theouter extent of the bundled optical fiber cable 10′ and thus a diameterD′ of the bundled optical fiber cable 10′. As can be seen in FIG. 5 ,the central cable unit 12 is substantially similar to the central cableunit 12 shown in FIG. 2 in that the central cable unit 12 of FIG. 5includes optical fibers 20 arranged in a stack 21 of ribbons 22. In FIG.5 , though, the stack 21 of ribbons 22 is disposed within a buffer tube42. Further, in the embodiment of FIG. 5 , the drop cables 14 are aplurality of buffer tubes 28 containing optical fibers 20. The exteriorsurfaces 31 of the buffer tubes 28 are in contact with the outer surface18 of the cable jacket 16. In embodiments, the buffer tubes 28 arestranded around the central cable unit 12 in a helical winding, such asan S winding, a Z winding, or an SZ winding.

Further, as can be seen in FIG. 5 , by using buffer tubes 28 as the dropcables 14, more drop cables 14 can be provided around the exterior ofthe central cable unit 12. In the embodiment depicted in FIG. 5 ,twenty-two buffer tubes 28 are provided around the central cable unit12. The buffer tubes 28 are accessed by cutting into the bundle jacket40 at specific access locations. In this embodiment, a buffer tube 28 isremoved from the bundle jacket 40 at a desired location and then splicedinto a tether cable (e.g., a FlexNAP™ system cable available fromCorning Incorporated, Corning, N.Y.). Thus, while splicing is performedin this embodiment at drop locations, the bundled optical fiber cable10′ provides the advantage that the central cable unit 12 does not haveto be accessed in performing the splice, thereby simplifying thesplicing procedure.

The buffer tubes 28 shown in FIG. 5 are substantially similar to thebuffer tubes 28 shown in FIG. 3 and, therefore, can contain, e.g., fromone to thirty-six optical fibers 20. As compared to the bundled opticalfiber cable 10 of FIG. 2 in which each drop cable 14 is provided with aseparate drop cable jacket 34, the bundled optical fiber cable 10′ ofFIG. 5 allows for more buffer tubes 28 by providing a single bundlejacket 40 for all the buffer tubes 28. In this way, the bundled opticalfiber cable 10′ of FIG. 5 is potentially able to provide a higheroptical fiber count than the bundled optical fiber cable 10 of FIG. 2 ina package that is roughly the same size, i.e., D≈D′.

FIG. 6 depicts an embodiment of a drop cable 14 having rodentprotection. The drop cable 14 includes a plurality of optical fibers 20disposed within a buffer tube 28. On an exterior surface 31 of thebuffer tube 28, an armor layer 44 is provided. In embodiments, the armorlayer 44 is a metallic tape wrapped around the buffer tube 28. Incertain embodiments, the metallic tape is corrugated. In otherembodiments, the armor layer 44 is stranded metal wire. In embodiments,the metal for the ribbon or wire includes at least one of steel oraluminum. The armor layer 44 is disposed within the drop cable jacket34. In embodiments, a hard polymer coating 46 is applied to the dropcable jacket 34 in addition to or in lieu of the armor layer 44. Inembodiments, the hard polymer coating 46 includes at least one of nylon,polyether ether ketone (PEEK), phenolic resins, polyetherimide (PEI),acrylates, acetals, etc. The material for the armor layer 44 and/or hardpolymer coating 46 is selected based on desired resistance levels,installation environment, flexibility, weight, and/or cost.

Advantageously, by providing each drop cable 14 with an armor layer 44and/or hard polymer coating 46, the aggregate effect is to also protectthe central cable unit 12. That is, the central cable unit 12 does notneed its own separate armor layer 44 or hard polymer coating 46 becausethe drop cables 14 that are wound around the central cable unit 12combine to provide rodent protection for the central cable unit 12.Further, considerable stiffness in the bundled optical fiber cable 10 isalleviated in this embodiment by through stranding the rodent protectionaround the central cable unit 12 via the drop cables 14.

FIG. 7 schematically depicts an exemplary deployment for the bundledoptical fiber cable 10 or bundled optical fiber cable 10′. For thepurposes of discuss, the bundled optical fiber cable 10 will bereferenced with respect to FIG. 7 . As shown therein, the bundledoptical fiber cable 10 supplies information to a telecommunicationnetwork 100, such as a 4G or 5G network. In the telecommunicationnetwork 100, the central cable unit 12 runs a length L from a first end12 a to a second end 12 b. In this way, the central cable unit 12 is an“express fiber” that transports data from node to node in thetelecommunication network 100. That is, the central cable unit 12 is nottapped with cable tethers along its length. Instead, the drop cables 14terminate at various points along length L of the central cable unit 12.As shown, a first drop cable 14 a terminates at a first antenna 105 a, asecond drop cable 14 b terminates at a second antenna 105 b, and a thirddrop cable 14 c terminates at a third antenna 105 c.

In embodiments, each drop cable 14 a, 14 b, 14 c is pre-connectorizedwith, e.g, a multi-fiber push on (MPO) connector, such as an MTP®Connector, a mechanical transfer (MT) connector, such as an OptiTip®Connector, or a single-fiber connector, such as an OptiTap® connector(all available from Corning Incorporated, Corning, N.Y.). In this way,the drop cables 14 a, 14 b, 14 c can easily be connected to a respectiveconnection terminal 110 a, 110 b, 110 c at each antenna 105 a, 105 b,105 c.

FIG. 9 schematically depicts a drop cable 14 separated from the bundledoptical fiber cable 10 at a drop location. As can be seen the drop cable14 is pre-connectorized with a connector 150. Leading up to the droplocation, a length of the drop cable 14 is removed from the drop cables14 wound around the bundled optical fiber cable 10, and at the locationof removal, the drop cable is stabilized with a tap protector 160, whichhelps prevent the separated drop cable 14 from unwinding from thebundled optical fiber cable 10 more than is desired during theinstallation process. The connector 150 of the pre-connectorized dropcable 14 is then connected to a tether cable (e.g., FlexNAP™ systemcable tether) or a terminal (e.g., OptiSheath™ MultiPort Terminalavailable from Corning Incorporated, Corning, N.Y.) at a pole 170, e.g.,for one of the connection terminals 110 a, 110 b, 100 c as shown in FIG.7 , to provide data transmission.

Referring again to FIG. 7 , an electrical grid tap 120 may be providedin embodiments at an antenna, such as antenna 105 b. The electrical gridtap 120 provides power to the antenna 105 b. In certain embodiments, theability to provide an electrical grid tap 120 for an antenna may belimited based on the location of the antenna. Advantageously, inembodiments, the bundled optical fiber cable 10 includes one or moreelectrical drop cables 130 that can be used to connect an electricalgrid tap 120 of an antenna, such as antenna 105 b, to other antennas inthe telecommunication network 100, such as antennas 105 a, 105 c.

In general, the drop cables 14 have a first end that begins at the firstend 12 a of the central cable unit 12 (i.e., the first ends of the dropcables 14 and the central cable unit 12 are coterminal), and the dropcables 14 have a second end that terminates before the second end 12 bof the central cable unit 12, particularly at a specified tap location.For the rest of the length of the central cable unit 12, a “dummy cable”may be run in place of the terminated drop cable 14 to maintainconsistent spacing of the remaining drop cables 14 around the centralcable unit 12, to maximize crush performance of the bundled opticalfiber cable 10, and/or to maintain a round profile for the bundledoptical fiber cable 10, which makes it better suited to encapsulationmethods and enhances operability with cable hardware. Thus, the dummycable is just a length of material containing a low cost filler so as toprovide a structure similar in diameter and/or mechanical properties tothe drop cables 14. For example, after drop cable 14 a reaches the tappoint located at antenna 105 a, a dummy cable may run in place of thedrop cable 14 a for the remaining length of the central cable unit 12.

However, in embodiments, an electrical drop cable 130 is used instead ofa dummy cable and/or instead of an optical fiber drop cable 14 so thatthe electrical drop cable 130 can provide electrical communicationbetween various points along the length of the bundled optical fibercable 10. The electrical drop cable 130 can be any of a variety ofsuitable cables for transmission of electrical power. In embodiments,the electrical drop cable 130 includes one or more conductive wires,such as copper or aluminum wires, disposed within an electricallyinsulating jacket material. As shown in FIG. 7 , an electrical dropcable 130 is provided after the termination of the first drop cable 14 aand after the termination of the second drop cable 14 b. One electricaldrop cable 130 links the electrical grid tap 120 of antenna 105 b to theconnection terminal 110 a of antenna 105 a, and another electrical dropcable 130 links the electrical grid tap 120 of antenna 105 b to theconnection terminal 110 c of antenna 105 c. Further, the electrical dropcables 130 provide the same benefits as the dummy cable but also theadditional benefit of providing electrical communication or powerdelivery along the length of the bundled optical fiber cable 10.

As alluded to, in embodiments, the bundled optical fiber cable 10 mayinclude electrical drop cables 130 beginning at the first end 12 a ofthe central cable unit 12 in place of optical fiber drop cables 14,i.e., not just as filler cables after termination of a drop cable 14. Insuch embodiments, the bundled optical fiber cable 10 may also useelectrical drop cables 14 as filler cables. Thus, the bundled opticalfiber cable 10 can be designed to provide convenient electricalcommunication and/or power transmission to a variety of drop locations,including optical fiber drop locations and non-optical fiber droplocations.

As shown in FIG. 7A, electrical drop cables 130 may also begin at thesecond end 12 b of the bundled fiber optic cable 10. In this regard,electrical power may be provided from a central location at second end12 b to coordinate with specific predetermined access points 13 whereeach of the optical drop cables 14 terminate. In this regard, opticalsignals may be sourced from a first end 12 a of the fiber optic cable 10and electrical power may be sourced from a second end 12 b of the fiberoptic cable 10. This bidirectional optical and electrical drop cablearrangement provides for optical and electrical termination at thepredetermined locations 13 along the fiber optic cable 10 whilemaintaining essentially the same cross-sectional footprint. For example,viewing the fiber optic cable 10 from the first end 12 a, for example,as an optical fiber drop cable 14 a terminates, an electrical drop cable130 a running from the direction of the second end 12 b of the fiberoptic cable 10 may substantially fill the cross-sectional area thatwould have been occupied had the optical fiber drop cable 14 a continuedthrough toward the second end 12 b of the central cable unit 12 beyondthe specific predetermined location 13 a. Similarly, looking at thefiber optic cable 10 from the second end 12 b, for example, as anelectrical drop cable 130 c terminates, an optical fiber drop cable 14 crunning from the direction of the first end 12 a of the central cableunit 12 may substantially fill the cross-sectional area that would havebeen occupied had the electrical drop cable 130 c continued throughtoward the first end 12 a of the cable 10 beyond the specificpredetermined location 13 c. Moreover, the cable 10 may comprisecombinations of electrical drop cables 130 that start and run from onlyone end of the cable 10 and/or are provided as shown in FIG. 7 , whereinthe electrical drop cables 130 may be injected into the cable footprintat discrete locations along the central cable unit 12 to tap into localpower at discrete locations along the cable 10.

Each electrical drop cable 130 may comprise a stranded pair of copperconductor wires, for example. One or more of the electrical drop cables130 may terminate at a predetermined location 13 along the length of thecable 10, depending on the power needs specific to that location. Bypre-engineering the cable 10 with power needs in mind, specific gaugeconductors may be provided to specific predetermined locations 13. Inthis regard, the gauge of the twisted pair electrical drop cables 130may all be the same or may vary in accordance with the specific powerneeds at a particular location 13. These discrete point-to-pointelectrical drop cables 130 may be terminated with conventional copperconnectors or be left as bare cable ends for field termination.Moreover, a short copper preconnectorized electrical drop cable may bespliced at each specific predetermined location 13 to access aparticular electrical drop cable 130. The access point may then beprotected with an overmolded enclosure similar to the type described inU.S. Pat. No. 7,127,143, incorporated herein by reference.

As shown in FIG. 7A at predetermined location 13 c, the electrical dropcable 130 c and fiber optic drop cable 14 c may each include an overlapportion 15 c and 131 c. Overlap portions 15 c and 131 c may be requiredto ensure that optical and electrical signals can be received at adiscrete distance away from the cable 10 at each predetermined location13. For example, fiber optic drop cable 14 c may have an overlap portion15 c that extends a distance x and electrical drop cable 130 c may havean overlap portion 131 c that extends a distance y. Distance x anddistance y may be substantially equal if desirable to deliver opticaland electrical signals to, for example, an optical and power terminal,that is essentially the same point a certain distance x or y away fromthe cable 10. However, distance x and distance y may be varied ifoptical signals and power are to be delivered to different points fromthe cable 10 at the predetermined location 13.

As shown in FIG. 7A, the electrical drop cable 130 c may be folded backon itself and secured to the central cable unit 12 with adhesive tape, aheat-shrink sleeve, or any other suitable covering to provide anti-snagcapability and protection during manufacture, transport, and install.

In accordance with other aspects of the present disclosure, as shown inFIG. 7B, both the fiber optic drop cables 14 and the electrical dropcables 130 may be in a stranded configuration. At each predeterminedlocation 13, where at least one electrical drop cable 130 and/or atleast one optical fiber drop cable 14 are separated from the bundledcable 10, the anti-snag covering 135 may be provided. The covering 135may be provided to cover all or a portion of the overlaps 15 c and 131c, including any connectors provided on the end of the cables 14 and130. Moreover, as shown in FIG. 7B, the electrical drop cable 130, forexample, may be brought back on itself by helical winding in a reversedirection around the perimeter of cable 10. This may avoid subjectingthe electrical drop cable 130 to pinching and allow a smaller footprintfor the cross-sectional area of the cable 10.

With regard to helically stranding an electrical drop cable 130 into atapered cable 10 as shown in FIG. 7B, if multiple layers of strandedfiber optic drop cables 14 are provided, introduction of electrical dropcables 130 into each stepped layer must be considered to avoid one ormore electrical drop cables 130 preventing easy separation of a fiberoptic drop cable 14 from the bundle due to the electrical drop cable 130being helically wrapped around the entire layer of fiber optic dropcables 14.

Upon reaching the second end 12 b of the central cable unit 12, thefibers contained within the central cable unit 12 may be spliced to theoptical fibers of another downstream section of bundled optical fibercable 10. In particular, optical fibers from the central cable unit 12may be spliced into the optical fibers of a second section of downstreamdrop cables 14 and into the optical fibers of a second section of adownstream central cable unit 12. In this way, successive bundledoptical fiber cable 10 sections may taper in terms of the number ofoptical fibers contained in the central cable unit 12, including down tozero optical fibers contained in the central cable unit 12. Inembodiments with zero optical fibers in the central cable unit 12, thecentral cable unit 12 may simply contain a strength member (or otherfiller rod) surrounded with a jacket material to provide a central cableunit 12 of a desired diameter. For example, a first section of bundledoptical fiber cable 10 may contain 864 optical fibers in the centralcable unit 12. In a second section of the bundled optical fiber cable10, 432 optical fibers of the 862 optical fibers may be extracted andspliced into drop cables 14 of the second section, and the remaining 432fibers, for example, may continue in the central cable unit 12 of thesecond section. This tapering continues until all of the remainingoptical fibers of the penultimate section of the bundled optical fibercable are divided among drop cables 14 in the final section, and thesedrop cables 14 may be carried by a central cable unit 12 that consistsonly of a jacketed strength member. While the example considered halvingthe number of optical fibers between successive sections of a bundledoptical fiber cable 10, the number of optical fibers extracted from thecentral cable unit 12 can vary depending on the needs of a particularapplication. In general, only so many optical fibers as are needed for aparticular section are extracted from the central cable unit 12.

Table 1, below, provides examples of final sections of the bundledoptical fiber cable 10 in which the final section of the central cableunit 12 is jacketed strength member. In each of the examples provided,the size of the strength member is the same and only the thickness ofthe jacket changes to accommodate the number of drop cables. In eachembodiment, the drop cables 14 considered are 4.8 mm in diameter andcontain from 4 to 12 optical fibers. Going from the 6-Position Cable(i.e., cable with six drop cables 14) to the 10-Position Cable, thenumber of optical fibers that can be carried goes from as low as 24 toas high as 120; although, not all of the drop cables 14 need to befilled. As can also be seen, the outer diameter of the bundled opticalfiber cable 10 for that section goes from 15.0 mm to 21.6 mm as thenumber of drop cables 14 increase from six to ten.

TABLE 1 Examples of Final Section of Bundled Optical Fiber Cable6-Position 8-Position 10-Position Cable Cable Cable Drop Cables 6 8 10Optical Fibers per Drop Cable  4 to 12  4 to 12  4 to 12  Total OpticalFibers 24 to 72 32 to 96 40 to 120 Drop Cable diameter (mm) 4.8 4.8 4.8Bundle diameter (mm) 15.0 18.0 21.6

Embodiments of the bundled optical fiber cable disclosed herein providecertain advantages over existing technology involving cable splicing. Inparticular, tap points in a network need to be precisely known before acable can be designed to reach each of the tap points. Because these arespecific locations, detailed engineering is required to measure theselocations and design the network precisely, which means that cablescannot be made until such designs are submitted to the manufacturer.Where splicing is used to provide tether cables, each tap point alongthe distribution cable length will need to be marked at the accesslocations, and then each individual access location will need to have atether spliced into the distribution cable. This process is timeconsuming and risky in that, each time this cable is accessed, the riskof cutting the wrong fibers or making a mistake increases. In thepresently disclosed bundled optical fiber cable, drop cables are woundaround the outside of the central cable unit, avoiding the need toaccess the cable interior and the associated risk of fiber cuts.

Further, in telecommunication networks, the increased demand for networkspeed leads to development of a denser network, i.e., a network havingmore access points and more fiber. In practice, this means that morecables need to be run through fiber ducts. Because the necessary fiberdensity for a particular development is difficult to predict, it isbeneficial to provide express lines in the network. In general, though,the amount of fiber that can be run through a duct is limited. Forexample, in two inch duct, a limit of 432 fibers was recognized in theindustry based on allowable fill ratios for the duct during a pulling orair blowing installation. As disclosed herein, the bundled optical fibercables provide an express line in such a way that it is feasible to fitfiber counts greater than 432 fibers into two inch duct whilemaintaining a fill ratio of at most 85% and while also offering apreconnectorized solution. Indeed, in embodiments of the presentlydisclose bundled optical fiber cable, 864 fibers can run through a twoinch duct. In this way, after exhaustion of the drop cables, the expressline fibers in the central cable unit can be spliced into the dropcables and central cable unit of a further section of a bundled opticalfiber cable if additional demand develops. Further, embodiments of thebundled optical fiber cable are flexible in their design in that thedrop cables can be electrical drop cables and/or back filled withelectrical drop cables after termination of an optical drop cable.

Unless otherwise expressly stated, it is in no way intended that anymethod set forth herein be construed as requiring that its steps beperformed in a specific order. Accordingly, where a method claim doesnot actually recite an order to be followed by its steps or it is nototherwise specifically stated in the claims or descriptions that thesteps are to be limited to a specific order, it is in no way intendedthat any particular order be inferred. In addition, as used herein thearticle “a” is intended include one or more than one component orelement, and is not intended to be construed as meaning only one.

It will be apparent to those skilled in the art that variousmodifications and variations can be made without departing from thespirit or scope of the disclosed embodiments. Since modificationscombinations, sub-combinations and variations of the disclosedembodiments incorporating the spirit and substance of the embodimentsmay occur to persons skilled in the art, the disclosed embodimentsshould be construed to include everything within the scope of theappended claims and their equivalents.

What is claimed is:
 1. A telecommunications network comprising: aplurality of network nodes; a bundled optical fiber cable, comprising: acentral cable unit spanning a first length from a first end to a secondend, the central cable unit comprising a first plurality of opticalfibers disposed within a cable jacket, wherein the central cable unitconnects two nodes of the plurality of network nodes; and a plurality ofoptical fiber drop cables wound around the cable jacket of the centralcable unit, each optical fiber drop cable spanning a different lengthfrom a first end to a second end and having one or more optical fibersdisposed within a buffer tube, wherein the second end of each opticalfiber drop cable is pre-connectorized with an optical fiber connector;wherein the first length spanned by the central cable unit is longerthan each different length of the plurality of optical fiber drop cableswhen the first end of each of the plurality of optical fiber drop cablesand the first end of the central cable unit are substantiallycoterminal; at least one connection terminal, wherein the optical fiberconnector of at least one of the optical fiber drop cables is connectedto the at least one connection terminal; and a plurality of antennas,wherein at least one optical fiber drop cable of the plurality ofoptical fiber drop cables terminates at each respective antenna of theplurality of antennas.
 2. The telecommunications network of claim 1,wherein each antenna of the plurality of antennas is associated with atleast one connection terminal, and wherein the optical fiber connectorof each respective optical fiber drop cable is connected to therespective connection terminal.
 3. The telecommunications network ofclaim 1, further comprising at least one tether cable, wherein theoptical fiber connector of at least one of the optical fiber drop cablesis connected to the at least one tether cable.
 4. The telecommunicationsnetwork of claim 1, wherein the bundled optical fiber cable furthercomprises one or more electrical drop cables for providing power to atleast one antenna of the plurality of antennas.
 5. Thetelecommunications network of claim 1, wherein each optical fiberconnector is selected from one of an MPO connector, an MT connector, ora single-fiber connector.
 6. A telecommunications network, comprising: aplurality of network nodes; a bundled optical fiber cable, comprising: acentral cable unit spanning a first length from a first end to a secondend, the central cable unit comprising a first plurality of opticalfibers disposed within a cable jacket, wherein the central cable unitconnects two nodes of the plurality of network nodes; and a plurality ofoptical fiber drop cables wound around the cable jacket of the centralcable unit, each optical fiber drop cable spanning a different lengthfrom a first end to a second end and having one or more optical fibersdisposed within a buffer tube; and a drop location where at least oneoptical fiber drop cable of the plurality of optical fiber drop cablesis separated from the bundled optical fiber cable, wherein a tapprotector is provided at the drop location to prevent the at least oneseparated optical fiber drop cable from unwinding from the bundledoptical fiber cable, and wherein the first length spanned by the centralcable unit is longer than each different length of the plurality ofoptical fiber drop cables when the first end of each of the plurality ofoptical fiber drop cables and the first end of the central cable unitare substantially coterminal.
 7. The telecommunications network of claim1, wherein the first plurality of optical fibers of the central cableunit are arranged in a stack of ribbons.
 8. The telecommunicationsnetwork of claim 7, wherein the stack of ribbons comprises a first stacksection, a second stack section, and a third stack section disposedbetween the first stack section and the third stack section, wherein thefirst stack section and the second stack section contain the same numberof optical fibers, and wherein the third stack section contains morethan the first stack section and the second section.
 9. Thetelecommunications network of claim 1, wherein the first plurality ofoptical fibers is at least 288 optical fibers.
 10. Thetelecommunications network of claim 1, wherein each optical fiber dropcable of the plurality optical fiber drop cables further comprises adrop cable jacket.
 11. The telecommunications network of claim 10,wherein each optical fiber drop cable of the plurality optical fiberdrop cables further comprises an armor layer between the buffer tube andthe drop cable jacket.
 12. The telecommunications network of claim 10,wherein each optical fiber drop cable of the plurality optical fiberdrop cables further comprises a hard polymer coating disposed around thedrop cable jacket, wherein the hard polymer coating comprises at leastone of nylon, polyether ether ketone, phenolic resins, polyetherimide,an acrylate, or an acetal.
 13. The telecommunications network of claim1, wherein each optical fiber drop cable of the plurality optical fiberdrop cables comprises up to thirty-six optical fibers.
 14. Thetelecommunications network of claim 1, wherein the bundled optical fibercable comprises up to twenty-four optical fiber drop cables.
 15. Thetelecommunications network of claim 1, wherein the one or more opticalfibers of each drop cable of the plurality of drop cables are arrangedin a rollable ribbon.
 16. The telecommunications network of claim 1,further comprising bands placed at various intervals along the bundledoptical fiber cable to keep the plurality of drop cables wrapped aroundthe central cable unit.
 17. The telecommunications network of claim 1,further comprising webbing provided around the plurality of drop cablesto keep the plurality of drop cables wrapped around the central cableunit.